I. Field of the Invention
The present invention relates generally to angle sensors and, more particularly, to an angle sensor between an input shaft and an output shaft.
II. Description of Related Art
In steering systems of the type used in automotive vehicles, the steering system typically includes an input shaft connected to the steering wheel. The input shaft is then connected to an output shaft through a torsion bar and the output shaft, in turn, is mechanically connected through linkage to the vehicle wheels. Consequently, rotation of the steering wheel pivots the wheels of the automotive vehicle through the torsion bar, output shaft, and steering linkage.
In many situations, it is highly desirable to determine the angular deflection between the input shaft and output shaft of the steering mechanism. The degree of angular deflection between the input shaft and output shaft, i.e. the angular deflection of the torsion bar, is utilized by the vehicle management system to determine the steering wheel torque and the amount of assist provided by the power steering. For example, rotation of the vehicle if stopped or nearly stopped, e.g. during a vehicle parking situation, typically creates a relatively high angular deflection between the input and output shaft thus calling for increased power assistance for turning the vehicle wheels. This deflection, furthermore, rarely exceeds about 20 degrees.
In addition to the angular deflection between the input shaft and output shaft of the steering, in many situations it is desirable to know the angular position of the vehicle wheels. Since the steering wheel typically can completely rotate three to four revolutions, it is necessary to keep track of the revolution count in order to determine the absolute angular position of the vehicle wheels.
There have been previously known systems which are capable of monitoring the angular deflection between the input and output shafts of the steering wheel. These previously known systems typically employ a transducer which measures the angular torque between the steering input and output shafts. However, since the steering output shaft can rotate up to three or four times, it has been necessary for the previously known devices to provide a long length of electrical cable, typically ribbon cable, within the steering column. Sufficient ribbon cable was provided so that the ribbon cable could wind around the steering column two or three times to accommodate multiple rotations of the steering wheel.
This previously known solution, however, has not proven wholly satisfactory in use. For example, it is possible for the electrical connector to become entangled after extended use which can entrap or even destroy the electrical connection between the cable and the angle sensor between the steering input and output shafts. When this occurs, the overall operation of the torque sensor for the steering system is compromised.
Similarly, there have been previously known systems which provide an output signal representative of the angular position of the vehicle wheels during multiple rotations of the steering wheel. These previously known systems, however, have proven to be unduly complex and expensive in construction.